Peter Frost's anthropology blog, with special reference to sexual selection and the evolution of skin, hair, and eye pigmentation

Saturday, June 18, 2011

More on French Canadians and Tay Sach's

French Canadian habitants playing at cards (Cornelius Krieghoff). With fewer British merchants than elsewhere, eastern Quebec was a land of opportunity for business-minded French Canadians. Did this selection affect the local gene pool?

When discussion turns to Tay Sach’s, people automatically think of the Jewish community. Yet this inherited illness reaches high levels in other human populations, particularly French Canadians.

Tay Sach’s has three unusual characteristics among French Canadians:

1. It is highly localized geographically, being concentrated in eastern Quebec. In Rimouski, the heterozygote frequency is 7.6%, versus 4.2% among Ashkenazi Jews and 0.3% among French Canadians in Montreal (De Braekeleer et al, 1992).

2. It is caused by two separate mutations: one that arose on the north shore of the St. Lawrence (Charlevoix and Saguenay-Lac Saint-Jean) and another that arose on the south shore (Bas Saint-Laurent) (Zlotogora, 1994).

3. It is relatively recent in origin, being absent in France. Neither mutation can be more than three centuries old and both probably postdate the British conquest of Quebec (1759).

These three characteristics argue for some kind of selective advantage, and not a random founder effect. Among Ashkenazi Jews, the selective advantage seems to be improved mental processing. Indeed, Tay Sach’s is one of four different genetic illnesses that are unusually common among Ashkenazim and that affect the same metabolic pathway in brain tissues (lysosomal storage). Homozygotes suffer neurological degeneration, mental retardation, and other neural problems. Heterozygotes, however, may be better at mentally demanding occupations (Cochran et al., 2006; Frost 2007; Murray, 2007; Zlotogora, 1994).

Interestingly, Tay Sach’s co-occurs in eastern Quebec with another hereditary illness that lies in the same metabolic pathway, i.e., lysosomal storage.

The mucolipidoses are composed of four distinct clinical conditions (designated type I–IV) that result from the accumulation of lipid and carbohydrate molecules due to specific lysosomal enzyme defects. (...) In the absence of this step, lysosomal enzymes are incorrectly routed into the extracellular space. This disorder is rare, with an estimated incidence of 1 in 640 000 births, although it may be higher in Saguenay-Lac-St Jean, a French Canadian isolate. (Ekstrand & Sankar, 2009, p. 603)

Are lysosomal storage illnesses common in eastern Quebec for the same reason that they are common among Ashkenazi Jews? At first thought, the idea may seem absurd. Weren’t French Canadians historically a nation of farmers? And didn’t British merchants fill all of the mentally demanding occupations?

In reality, things were not so simple. There was always a French-Canadian middle class, particularly wherever British merchants were few and far between. They were especially rare in those parts of eastern Quebec that today have high rates of Tay Sach’s (Charlevoix, Saguenay-Lac Saint-Jean, Bas Saint-Laurent). This rarity came to the notice of Alexis de Tocqueville while passing through Bas Saint-Laurent in 1831:

In this portion of Canada, one does not hear English at all. The population is only French, and yet when one encounters an inn, or a merchant, the sign is in English.(De Tocqueville, 2003, p. 185).

This lack of English competition opened up an enviable niche for French Canadians—or rather for those with the right aptitudes, especially in numeracy, literacy, and bilingualism. Elsewhere, these niches were filled by British immigrants, particularly in Montreal, Quebec City, the Eastern Townships, the Ottawa valley, and the southern and eastern shorelines of the Gaspé Peninsula.

This point is made in a study of the life of John Guay (1828-1880), a leading French Canadian merchant in the Saguenay region. To enter this occupational niche required a special mental toolkit:

Success in trade was never easy because of the competition, the fragility of the markets, and the instability of business conditions. The ablest managed to live or survive. Others, the greatest number, closed shop after a few years. Only those possessing exceptional qualities would make a fortune.(Lapointe, 1996, p. 3)

But the payoff was huge. John Guay had ten children who survived to adulthood—twice the mean reproductive success of his French Canadian contemporaries. Lapointe (1996, p. 126) attributes Guay’s success in business to the mental outlook he displayed from an early age:

The evolution of market capitalism has given rise to rules that a businessman cannot evade. One cannot simply improvise as a merchant. It takes talent and of course capital. Spontaneous generation was very uncommon in 19th-century Quebec, indeed nonexistent in John Guay’s case. The family environment in which he grew up predisposed him to develop an interest and also aptitudes for the businesses of trade, forestry, and farming. His successful career henceforth proved that a French-Canadian merchant could ably penetrate the world of business; a world where, let us remember, English Canadians controlled most of the commercial and industrial activities.

The Beauce exception

One region in eastern Quebec, however, has always been solidly French Canadian and yet has low incidences of Tay Sach’s and mucoliposes. This is Beauce County, a region south of Quebec City that covers the Chaudière valley up to the American border. Furthermore, Beaucerons are stereotyped as being self-reliant, business-minded go-getters—the “Yankees” of Quebec.

Beauce County nonetheless differs demographically from the rest of eastern Quebec in one respect. Settlement began earlier there than elsewhere, well before the Conquest. There was thus a larger pool of people and hence more individuals who could fill the niches that opened up after the Conquest, as Quebec moved from a semi-feudal mercantilist society to a more market-driven economy. Selection thus had more leeway to favor individuals who had the necessary aptitudes while not suffering the costs that lysosomal storage illnesses impose on homozygotes.

Fast evolution?

All of this might seem hard to believe. How could such selection operate over a time span of less than two centuries? Yet that is what the data tell us. Neither of these Tay Sach’s mutations is present in France. They must have gone from zero to their current high prevalence in less than ten generations.

13 comments:

This is very interesting. The French half of my family comes from the Trois Rivieres region.

Two hundred years may be enough for significant genetic change. A Russian scientist domesticated wild foxes in less than 20 generation. Two hundred years is about 10 human generations.

Also, French Canadians were isolated from their English masters even in Western Quebec. The total number of French immigrants to Quebec was only about 10,000 (almost everyone claims descent from Louis Hebert), so the evolving the population was almost a bottleneck.

Beauce County "Selection thus had more leeway to favor individuals who had the necessary aptitudes while not suffering the costs that lysosomal storage illnesses impose on homozygotes. [...] Beauce County, a region south of Quebec City that covers the Chaudière valley up to the American border."

One aspect of Beauce County that may have been significant is its location, handy for the Loyalists who were kicked out of the US after 1776. Here is an interesting one with Beauce connections George Pozer

Your first question is easy to answer. To go from 0% to 7.6%, in terms of heterozygote frequency, the carriers must have had a clear reproductive advantage.

How much of an advantage? This is a question I hope to answer. There is genealogical information on Tay Sach's carriers. So it should be possible to calculate their mean fertility rate (although I'm more interested in the number of children who survived to adulthood). I also hope to find information on the occupational profile of carriers.

Sykes,

Yes, evolution can move a lot faster than most people think. Evolutionary psychologists in particular are handicapped by the idea that nothing special has happened since the Pleistocene.

Tod,

Yes, and there were also many German mercenaries who settled in Beauce County after fighting the American revolutionary army in and around Quebec City.

Anon,

Getting a book published is not easy. Most publishing houses will not consider a manuscript unless it's submitted by a literary agent. And it's impossible to get a literary agent unless you've already published.

I might be able to find an agent if my recently published book sells well (i.e., Femmes claires, hommes foncés : Les racines oubliées du colorisme).

As I understand it you're saying that over enough generations ordinary populations can supply genetically capable people who can fill the intellectually demanding occupations without the drawbacks of Tay Sach’s style alleles.

By my way of thinking Ashkenazim having a lot of these TS style alleles rather weighs against Ashkenazi genetic disease/IQ-associated alleles having been under selection for the extended period that Cochran and Harpending suggest. Bearing in mind what Cochran says about natural selection optimizing function; why would sub optimal quick fixes still be around a millenium later ?

(Of course the countervailing veiw would be that the Ashkenazim were in cutthroat competition with each other and needed all the edge they could get )

The homozygotes for disease/IQ alleles among the Ashkenazim must have been remarkably common, given their consanguineous marriages. Could this have caused parents to have extra children to compensate for the sickly homozygote children ?

Yes, the bigger the population, and the longer the time span, the greater the chance of getting an optimal package of adaptations.

Conversely, you get "quick fixes" when the population is small and moving into a new niche over a short span of time.

For Ashkenazi Jews, Greg sees this process beginning in the Middle Ages. I see it starting later, specifically in the 1600s when large numbers of Jewish craftsmen and craftswomen began to enter the "proto-industrial" niche, i.e., family-based cottage industries that produced on contract for urban merchants and that served relatively large and volatile markets.

I really don't know about your last question. Did people back then understand the genetic nature of Tay Sach's? Also, the main check on family size was the age of marriage. Men tended to marry once they had the means to support a family. If a young man came from an economically successful family, he could marry earlier and hence have a larger family.

According to 'A People That Shall Dwell Alone' Jewish people back then did understand that a family with several members suffering from a disease was not a family to be marrying into. Moreover the qualities of the brothers of a prospective bride were paid attention to (sex linked factors). A case of mental illness in the family was profoundly damaging to the marriage prospects of all family members.

"the main check on family size was the age of marriage. Men tended to marry once they had the means to support a family. If a young man came from an economically successful family, he could marry earlier and hence have a larger family."

The supreme resource for obtaining a good marriage was having scholars in the family tree (yikhus) which many could trace back six generations A good scholar could marry very young to the daughter of a successful businessman and be supported with free room and board (kest) as well as a large dowry.'Is my mother-in-law paralyzed that I should have to earn a living' Scholarship was more highly regarded than business success and although the two often went together businessmen supported the most eminent scholars to such an extent that many became wealthy in their own right.

I think there is something in the Talmudic scholarship theory of Ashkenazi intelligence.

I disagree with Kevin on this point. Before the 20th century, it was common practice to enquire about the family background of a prospective son-in-law or daughter-in-law. I'm not convinced that this was a specifically Jewish culture trait.

If we look at the demographic history of the Ashkenazi community, there was steady but sluggish growth until about 1600, when it may have numbered c. 200,000 individuals and then a rapid acceleration that ended around 1900. Was this demographic expansion due to a change in marital advice? No. It was due to a change in the economic environment that greatly increased the value of child labor in family-run workshops.

Maybe I've been too influenced by historical materialism. I agree that ideological factors are important, but their role here would have been secondary.

"Before the 20th century, it was common practice to enquire about the family background of a prospective son-in-law or daughter-in-law. I'm not convinced that this was a specifically Jewish culture trait."

I think your post on Asian IQ is consistant with Talmudic study being responsible for some of the Jewish superiority. (If it worked for the Imperial Mandrins why not Ashkenazim ?). ASPM and scribes too. It seems not unlikely to me that Jews have such a high verbal IQ because of selection for success in Talmudic scholarship and disputation.(There is a book called "What is Talmud?: the art of disagreement") Successful cottage industry entrepreneurship does not select for verbal ability or else the English would be also have IQs skewed to the verbal.

I don't doubt that demographic expansion due to a change in the value of child labor in family-run workshops is responsible for much of the IQ advantage, but I think the Ashkenazi intellect was was filtered through Jewish culture and further refined.

I half-agree with you. My main problem is that Jewish culture, i.e., Jewish marital practices, cannot explain the differences in mean IQ we see between Ashkenazim and Sephardim.

Also, your comparison with the Chinese civil service exam does not seem appropriate here, since success on that exam was key to entry into good-paying jobs and a number of other tangible benefits. A prospective father-in-law does not have the same leeway as the Chinese Empire to mobilize resources for family formation.

But, yes, I agree that marital practices were undoubtedly a critical factor.

"Jewish marital practices, cannot explain the differences in mean IQ we see between Ashkenazim and Sephardim."

I think that line of argument requires the Sephardim to never have been much smarter than gentiles and never have suffered a collective setback to their way of life that could account for the loss of that superiority.

The Sephardi did suffer a setback to their development but up until their expulsion from Spain they were clearly superior in IQ to gentiles and quite possibly every bit as clever as the Ashkenazim of that time. ( The success of the Conversos leaves no doubt about their genetic superiority (see Here p.180-82

success on that exam was key to entry into good-paying jobs and a number of other tangible benefits. A prospective father-in-law does not have the same leeway as the Chinese Empire to mobilize resources for family formation

An Ashkenazi noted as a scholar would not be be poor for long. He would received a range of valuable emoluments.

1. A wealthy man's daughter as wife.

2. Extremely high status in the community of a kind which brought economic benefits For example a ruling granted business monopolies on trade with gentiles to eminent scholars.

3. Gifts, even if a scholar was well-off.

4.Protection from anyone speaking against him. This was enforced by bans and fines.

My expectation is that the purported evolution of behavioral characteristics of Jews such as high intelligence are most likely associated with the evolution of virulence, which is founded on horizontal transmission. This is founded on their nation migrating through evolutionary time among multiple national territories. This, in turn, is founded on their ability to express their ethnic genetic interests despite being dispersed.

This would swamp any evolutionary pressures from being restricted to certain trades. Indeed, being restricted to trades such as finance would facilitate mobility and horizontal transmission.

"Indeed, being restricted to trades such as finance would facilitate mobility and horizontal transmission."

It's completely unclear what that means, JimBo never spells it out.

Anyway, the occupations of Jews did alter radically in the 16th century when 'Village Jews' appeared and the subsequent Jewish population explosion must have primarily resulted from the phenonomen Peter has identified:- "...specifically in the 1600s when large numbers of Jewish craftsmen and craftswomen began to enter the "proto-industrial" niche, i.e., family-based cottage industries that produced on contract for urban merchants and that served relatively large and volatile markets"

Welcome to my blog! For the most part, this page will be an extension of my website, with comments relating to my research. But it will also branch out into more general discussions of human evolution.